chapter 13 linear-digital ics. copyright ©2009 by pearson education, inc. upper saddle river, new...
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Chapter 13Linear-Digital ICs
Copyright ©2009 by Pearson Education, Inc.Upper Saddle River, New Jersey 07458 • All rights reserved.
Electronic Devices and Circuit Theory, 10/eRobert L. Boylestad and Louis Nashelsky
Linear Digital ICsLinear Digital ICs
ComparatorsComparatorsDigital/analog convertersDigital/analog converters
TimersTimersVoltage-controlled oscillatorsVoltage-controlled oscillators
Phase-locked loop circuitsPhase-locked loop circuitsInterface circuits Interface circuits
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Copyright ©2009 by Pearson Education, Inc.Upper Saddle River, New Jersey 07458 • All rights reserved.
Electronic Devices and Circuit Theory, 10/eRobert L. Boylestad and Louis Nashelsky
Comparator CircuitComparator Circuit
The operation is a basic comparison. The output swings between its maximum and minimum voltage, depending upon whether one input (Vin) is greater or less than the other (Vref).
The output is always a square wave where: • The maximum high output voltage is +VSAT. • The minimum low output voltage is –VSAT.
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Copyright ©2009 by Pearson Education, Inc.Upper Saddle River, New Jersey 07458 • All rights reserved.
Electronic Devices and Circuit Theory, 10/eRobert L. Boylestad and Louis Nashelsky
Noninverting Op-Amp ComparatorNoninverting Op-Amp Comparator
For a noninverting op-amp comparator:
• The output goes to +VSAT when input Vi is greater than the reference voltage.
• The output goes to –VSAT when input Vi is less than the reference voltage.
Example:Example:
• Vref in this circuit is +6V (taken from the voltage divider)• +VSAT = +V, or +12V• VSAT = V or –12V
When Vi is greater than +6V the output swings to +12V and the LED goes on. When Vi is less than +6V the output is at –12V and the LED goes off.
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Copyright ©2009 by Pearson Education, Inc.Upper Saddle River, New Jersey 07458 • All rights reserved.
Electronic Devices and Circuit Theory, 10/eRobert L. Boylestad and Louis Nashelsky
Inverting Op-Amp ComparatorInverting Op-Amp Comparator
For an inverting op-amp comparator:
• The output goes to –VSAT when input Vi is greater than the reference voltage.
• The output goes to +VSAT when input Vi is less than the reference voltage.
Example:Example:
• Vref in this circuit is +6V (taken from the voltage divider)• +VSAT = +V, or +12V• VSAT = V or –12V
When Vi is greater than +6V the output swings to –12V and the LED goes off. When Vi is less than +6V the output is at +12V and the LED goes on.
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Copyright ©2009 by Pearson Education, Inc.Upper Saddle River, New Jersey 07458 • All rights reserved.
Electronic Devices and Circuit Theory, 10/eRobert L. Boylestad and Louis Nashelsky
Comparator ICsComparator ICs
Advantages:
• Faster switching• Built-in noise immunity• Outputs capable of directly driving loads
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Copyright ©2009 by Pearson Education, Inc.Upper Saddle River, New Jersey 07458 • All rights reserved.
Electronic Devices and Circuit Theory, 10/eRobert L. Boylestad and Louis Nashelsky
Digital-Analog ConvertersDigital-Analog Converters
Types:
• Digital-to-analog converters (ADCs)• Analog-to-digital converters (DACs)
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Copyright ©2009 by Pearson Education, Inc.Upper Saddle River, New Jersey 07458 • All rights reserved.
Electronic Devices and Circuit Theory, 10/eRobert L. Boylestad and Louis Nashelsky
Digital-to Analog Converter:Digital-to Analog Converter:Ladder Network VersionLadder Network Version
ref4
33
22
11
00
o V2
2D2D2D2DV
4ref
2
V
Output Voltage, VOutput Voltage, Voo::
Voltage Resolution:Voltage Resolution:
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Copyright ©2009 by Pearson Education, Inc.Upper Saddle River, New Jersey 07458 • All rights reserved.
Electronic Devices and Circuit Theory, 10/eRobert L. Boylestad and Louis Nashelsky
Analog-to-Digital ConvertersAnalog-to-Digital Converters
Types:
• Dual Slope Conversion• Ladder Network Conversion
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Copyright ©2009 by Pearson Education, Inc.Upper Saddle River, New Jersey 07458 • All rights reserved.
Electronic Devices and Circuit Theory, 10/eRobert L. Boylestad and Louis Nashelsky
Analog-to-Digital ConversionAnalog-to-Digital ConversionDual Slope ConversionDual Slope Conversion
The analog input voltage is applied to an integrator or ramp-generator circuit.
The digital output is obtained from a digital counter that is operated during both positive and negative slope (ramp) intervals of the integrator.
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Copyright ©2009 by Pearson Education, Inc.Upper Saddle River, New Jersey 07458 • All rights reserved.
Electronic Devices and Circuit Theory, 10/eRobert L. Boylestad and Louis Nashelsky
Rising SlopeRising Slope
For a fixed interval the analog voltage is applied to the integrator. The integrator output rises to some positive level. This positive voltage is applied to a comparator. At the end of the fixed interval, the counter is reset to 0. An electronic switch connects the integrator input to a fixed input or reference voltage.
Falling SlopeFalling Slope
The integrator output decreases at a fixed rate. The counter advances during this time. When the integrator output (connected to the comparator input) falls below the reference level of the comparator, control logic stops the counter.The digital counter output is the digital conversion of the analog input.
Dual Slope ConversionDual Slope Conversion
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Copyright ©2009 by Pearson Education, Inc.Upper Saddle River, New Jersey 07458 • All rights reserved.
Electronic Devices and Circuit Theory, 10/eRobert L. Boylestad and Louis Nashelsky
A digital counter advances from zero while a ladder network converts the digital count to a staircase analog voltage.
When the staircase voltage into the comparator equals the analog input voltage, the counter stops.
The last count is the digital conversion of the analog input.
Ladder Network ConversionLadder Network Conversion
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Copyright ©2009 by Pearson Education, Inc.Upper Saddle River, New Jersey 07458 • All rights reserved.
Electronic Devices and Circuit Theory, 10/eRobert L. Boylestad and Louis Nashelsky
Resolution of Analog-to-Digital ConvertersResolution of Analog-to-Digital Converters
The resolution depends on the amount of voltage per step (digital bit):
nref
2
V
2.4mV2
10V
2
V12n
ref
Example:Example: A 12-bit ADC with a 10V reference level has the following resolution:
where n is the number of digital bits
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Copyright ©2009 by Pearson Education, Inc.Upper Saddle River, New Jersey 07458 • All rights reserved.
Electronic Devices and Circuit Theory, 10/eRobert L. Boylestad and Louis Nashelsky
f
2T
n
conv
where
Tconv = conversion time (seconds)n = number of binary bitsf = clock frequency for the counter
Analog-to-Digital Conversion Time Analog-to-Digital Conversion Time
The conversion time depends on the clock frequency of the counter.
Example:Example: A 12bit ADC with a 1MHz clock has a maximum conversion time.
4.1ms1MHz
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Copyright ©2009 by Pearson Education, Inc.Upper Saddle River, New Jersey 07458 • All rights reserved.
Electronic Devices and Circuit Theory, 10/eRobert L. Boylestad and Louis Nashelsky
555 Timer Circuit555 Timer Circuit
The 555 Timer is an example of a versatile Timer IC.
Astable OperationAstable Operation
The timer output is a repetitive square wave.The output frequency can be calculated as shown here.
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Copyright ©2009 by Pearson Education, Inc.Upper Saddle River, New Jersey 07458 • All rights reserved.
Electronic Devices and Circuit Theory, 10/eRobert L. Boylestad and Louis Nashelsky
Monostable OperationMonostable Operation
The timer output is a one shot pulse. When an input is received it triggers a one shot pulse. The time for which the output remains high can be calculated as shown.
555 Timer Circuit555 Timer Circuit
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Copyright ©2009 by Pearson Education, Inc.Upper Saddle River, New Jersey 07458 • All rights reserved.
Electronic Devices and Circuit Theory, 10/eRobert L. Boylestad and Louis Nashelsky
Voltage-Controlled OscillatorVoltage-Controlled Oscillator
The oscillator output is a variable frequency square wave or triangular wave. The output frequency depends on the modulation input voltage (VC).
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Copyright ©2009 by Pearson Education, Inc.Upper Saddle River, New Jersey 07458 • All rights reserved.
Electronic Devices and Circuit Theory, 10/eRobert L. Boylestad and Louis Nashelsky
The output frequency can be calculated as shown in the graph.
Note that the formula also indicates other circuit parameters that affect the output frequency.
566 Voltage-Controlled Oscillator566 Voltage-Controlled Oscillator
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Copyright ©2009 by Pearson Education, Inc.Upper Saddle River, New Jersey 07458 • All rights reserved.
Electronic Devices and Circuit Theory, 10/eRobert L. Boylestad and Louis Nashelsky
Phase-Locked LoopPhase-Locked Loop
The input signal is a frequency and the output signal is a voltage representing the difference in frequency between the input and the internal VCO.
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Copyright ©2009 by Pearson Education, Inc.Upper Saddle River, New Jersey 07458 • All rights reserved.
Electronic Devices and Circuit Theory, 10/eRobert L. Boylestad and Louis Nashelsky
Basic Operation of the Phase-Locked Loop Basic Operation of the Phase-Locked Loop
Three operating modes:
LockLockfi = fVCO
TrackingTracking
fi fVCO, but the fVCO adjusts until fVCO= fi
Out-of-LockOut-of-Lock
fi fVCO, and they never will be the same
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Copyright ©2009 by Pearson Education, Inc.Upper Saddle River, New Jersey 07458 • All rights reserved.
Electronic Devices and Circuit Theory, 10/eRobert L. Boylestad and Louis Nashelsky
Phase-Locked Loop: Lock ModePhase-Locked Loop: Lock ModeThe input frequency and the internal VCO output frequency are applied to the phase comparator.
If they are the same, the phase comparator output voltage indicates no error.
This no-error voltage is filtered and amplified before it is made available to the output.
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The no-error voltage is also applied to the internal VCO input to maintain the VCO’s output frequency.
Copyright ©2009 by Pearson Education, Inc.Upper Saddle River, New Jersey 07458 • All rights reserved.
Electronic Devices and Circuit Theory, 10/eRobert L. Boylestad and Louis Nashelsky
Phase-Locked Loop: Tracking ModePhase-Locked Loop: Tracking Mode
If the input frequency does not equal the VCO frequency then the phase comparator outputs an error voltage.
This error voltage is filtered and amplified and made available to the output.
The error voltage is also applied to the VCO input. This causes the VCO to change output frequency.
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This looping continues until the VCO has adjusted to the new input frequency and they are equal again.
Copyright ©2009 by Pearson Education, Inc.Upper Saddle River, New Jersey 07458 • All rights reserved.
Electronic Devices and Circuit Theory, 10/eRobert L. Boylestad and Louis Nashelsky
Phase-Locked Loop: Out-of-Lock ModePhase-Locked Loop: Out-of-Lock Mode
If the input frequency does not equal the VCO frequency and the resulting error voltage does not cause the VCO to catch up to the input frequency, then the system is out of lock. The VCO will never equal the input frequency.
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Copyright ©2009 by Pearson Education, Inc.Upper Saddle River, New Jersey 07458 • All rights reserved.
Electronic Devices and Circuit Theory, 10/eRobert L. Boylestad and Louis Nashelsky
Phase-Locked Loop: Frequency RangesPhase-Locked Loop: Frequency Ranges
Lock RangeLock Range—The range of input frequencies for which the VCO will track.
Capture RangeCapture Range —A narrow range of frequencies into which the input frequency must fall before the VCO can track. If the input frequency falls out of the lock range it must first enter into the capture range.
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Copyright ©2009 by Pearson Education, Inc.Upper Saddle River, New Jersey 07458 • All rights reserved.
Electronic Devices and Circuit Theory, 10/eRobert L. Boylestad and Louis Nashelsky
Phase-Locked LoopPhase-Locked Loop
Applications:
• FM demodulator• Frequency Synthesizer• FSK decoder
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Copyright ©2009 by Pearson Education, Inc.Upper Saddle River, New Jersey 07458 • All rights reserved.
Electronic Devices and Circuit Theory, 10/eRobert L. Boylestad and Louis Nashelsky
Interface CircuitryInterface Circuitry
Interface circuitry:
• Driving loads• Producing output signals at proper voltage
or current levels• Impedance matching• Strobing or timing signals
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Copyright ©2009 by Pearson Education, Inc.Upper Saddle River, New Jersey 07458 • All rights reserved.
Electronic Devices and Circuit Theory, 10/eRobert L. Boylestad and Louis Nashelsky
Interface Circuitry: Dual Line DriversInterface Circuitry: Dual Line Drivers
The input is TTL digital logic signal levels.
The output is capable of driving TTL or CMOS devise circuits.
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Copyright ©2009 by Pearson Education, Inc.Upper Saddle River, New Jersey 07458 • All rights reserved.
Electronic Devices and Circuit Theory, 10/eRobert L. Boylestad and Louis Nashelsky
RS-232-to-TTL ConverterRS-232-to-TTL Converter
The input is RS-232 electronic industry standard for serial communications.
The output will drive TTL circuitry.
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